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Thread: RF Exploring : HOw Noisy Are Our Components

  1. #1

    RF Exploring : HOw Noisy Are Our Components

    I've been using the hell out of this thing lately. I'm putting together a new rig, and while I had everything wired up on the bench to set up the OSD, I noticed the receiver RSSI would not drop below 50% with the radio off.

    I turned on the RF explorer and sure enough, the noise floor was off the charts, which explains the high RSSI. Yesterday I had a similar issue caused by my laptop, but this time the laptop wasn't running. I then started checking each component one by one to try to figure out the cause. You may find the results interesting..

    Span is set from 432-446MHz, scaled from -120dBm to -40dBm ("very loud!")
    Solid black plots are real time readings, plots showing a line above are peak hold mode. "Clearance" is how far I had to move the explorer back to no longer pick it up, so I'm assuming this is how far away it should be from your receiver to not affect it.

    This is not inside a faraday cage, and I am not an RF engineer. This is "putting stuff next to the explorer to see what happens" type science.

    Baseline, nothing powered
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    Punch RC brand ESC (80a, 5a SBEC), clearance 16"
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    PZ0420N 600TVL camera from securitycamera2000, clearance 14"
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    "800mw" 1280MHz with 1.3GHz low pass filter. No change to noise floor.
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    Skylark Tiny 2 OSD board, clearance over 3 feet!
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    Peak hold after a minute
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    Peak relative to background noise after unplugging battery
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    I am really hoping something is wrong with this OSD. It makes a faint high pitched whistle while powered, somewhat like an old tube TV. I thought maybe it was the switching frequency, however the last one we set up (mounted in my brother's plane) does not whistle or emit any of this hash.
    Last edited by Airborne; 28th February 2012 at 12:30 AM.

  2. #2
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    how far do you have to put the RF Explorer away from that osd to get the levels back to normal ?

  3. #3
    I had to hold the explorer at least 3 feet away to not pick it up.

    Only one of our Tiny 2's is doing this, the other one causes no visible changes to the noise floor in the 433-444 band, and does not have any other other issues described below.

    The same OSD module generating all this noise also:

    Shuts down my computer if connected to both the USB adapter and a battery at the same time. I had to remove the +5v lead coming from the receiver in order to calibrate it.

    Emits a faint but annoying high pitched whistle whenever powered

    Occasionally garbles the OSD text requiring the reset button to be pressed.

  4. #4
    Navigator Akoni's Avatar
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    Quote Originally Posted by sim_io View Post
    Where did you order yours from?
    Seeed Studio.

    http://www.seeedstudio.com/depot/hac...ent-c-174.html

  5. #5
    Navigator Akoni's Avatar
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    Quote Originally Posted by sim_io View Post
    Thanks Akoni, I wish there was a model that had 72Mhz to 5.8Ghz for all purpose fpv but I bet those are much bigger and really expensive.
    Most portable spec analyzers cost in multi-thousand dollar range so I v happy Ariel developed this unit.

  6. #6
    Professional spectrum analyzers cost tens of thousands of dollars.. the RF explorer is an outstanding deal even if it doesn't cover 72, 1.3 or 5.8!

    I have many more items I've "explored" to be added to this thread later on.

  7. #7
    KC8UD GLEvideo's Avatar
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    For what its worth...I use a Yeasu VR-500 receiver http://wiki.radioreference.com/index.php/File:Vr500.jpg to check a multitude of frequencies. While it is not a spectrum analyzer, it does provide a quasi spectrum display of a range of frequencies and signal strength of each signal. It covers from 150 KHz up to 1.3 Ghz. It's no longer in production but there are several out there on the used market. It's not a replacement for the spectrum analyzer but it gets you into other frequency ranges not covered by the RFExplorer and is a very useful receiver as well.
    Airplanes LIKE to fly : Helicopters WANT to kill you.

  8. #8
    Navigator Akoni's Avatar
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    Quote Originally Posted by GLEvideo View Post
    For what its worth...I use a Yeasu VR-500 receiver http://wiki.radioreference.com/index.php/File:Vr500.jpg to check a multitude of frequencies. While it is not a spectrum analyzer, it does provide a quasi spectrum display of a range of frequencies and signal strength of each signal. It covers from 150 KHz up to 1.3 Ghz. It's no longer in production but there are several out there on the used market. It's not a replacement for the spectrum analyzer but it gets you into other frequency ranges not covered by the RFExplorer and is a very useful receiver as well.
    Hmm, that's a cool idea. I haven't used my vr-500 in a long time but I still have it. I'll dig it up and have a look.

  9. #9
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    The 'whistle' is from something going on and off somewhere around 2-5 kHz. I don't own that OSD, but it might be because the switching power supply is underloaded.

  10. #10
    Who I am^^ Stuff I Say>> Reverand Blue Chip's Avatar
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    I did some testing as well....

    Interesting results....

    With 433 set as the mid point and +/- 20 as the range - my noise floor stuck right around -92.5 or so. With the Trace II plugged in - I got a definite spike at 432.102 - I did this more than a dozen times... here's the deal though - the spike was maxed at -87 (still at the 432.102). It definitely throws something off - but I'm not sure that it's enough to matter. Further - at anything more that 12" it became a non issue.

    For what it's worth - my Tiny II didn't throw anything.
    "He who turns himself into a beast gets rid of the pain of being a man. I became the God Damn Honey Badger." Visit me on YouTube "BlueChipFPV"

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